Physics Question Over 2 Dimensional Friction Problems

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Homework Help Overview

The discussion revolves around a physics problem involving a bucket being spun in a vertical circle, with a focus on forces acting on a glass placed inside the bucket. The problem explores concepts related to circular motion, centripetal force, and friction.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss drawing free-body diagrams and identifying forces acting on the glass at the top of the circle. There are questions about the direction of net force and the source of centripetal force. Some participants express confusion regarding the relationship between normal force and centripetal force.

Discussion Status

Several participants have provided insights into the forces involved, particularly the role of weight and normal force. Some have attempted calculations for the required speed to keep the glass from falling out and to prevent the string from breaking. There is ongoing exploration of the assumptions and definitions related to the forces at play.

Contextual Notes

Participants note the potential confusion arising from the problem's title mentioning friction, which may not directly apply to the current scenario. There are also varying interpretations of the forces acting on the glass, particularly when the normal force is zero.

  • #31
haruspex said:
The glass is blissfully unaware of the tension in the string and of gravity acting on the bucket. Which forces act directly on the glass, and by doing so provide the centripetal force ( so don't answer "centripetal force").

Normal Force?
 
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  • #32
Xazerd said:
Thank You, but I already solved that one now ( I got Net Force= Normal Force- Weight + (Mass*Velocity^2)/radius.)
That equation is not correct, in a couple of ways. Perhaps you've typed it out wrongly?
 
  • #33
pgardn said:
T + mg = (mv^2)/r
Think again. At what point in the loop is the tension greatest?
 
  • #34
haruspex said:
Think again. At what point in the loop is the tension greatest?

Aha again!

I was using the FBD for part a)

The problem said Maximum tension. This would happen at the bottom of the loop.

So T - mg = (mv^2)/r

It always helps to answer the questions that are actually asked.
Sorry to the OP. Thanks to Mr. H!
 
  • #35
pgardn said:
Aha again!

I was using the FBD for part a)

The problem said Maximum tension. This would happen at the bottom of the loop.

So T - mg = (mv^2)/r

It always helps to answer the questions that are actually asked.
Sorry to the OP. Thanks to Mr. H!

So is this the equation I use for part c and d, but I have to combine the mass of both the bucket and glass?
 
  • #36
Xazerd said:
So is this the equation I use for part c and d, but I have to combine the mass of both the bucket and glass?

Not for part c)

You got part c.

Gravity the sole actor for the centripetal force in c, so mass cancels.

Part d) would occur at the bottom of the circular path. So the tension, or more directly the normal force would act up, and gravity acts down. If you combine mass of the glass and the bucket then you can use tension.
 
  • #37
pgardn said:
Not for part c)

You got part c.

Gravity the sole actor for the centripetal force in c, so mass cancels.

Part d) would occur at the bottom of the circular path. So the tension, or more directly the normal force would act up, and gravity acts down. If you combine mass of the glass and the bucket then you can use tension.

Ok. Got it. Thanks!
 
  • #38
Xazerd said:
Ok. Got it. Thanks!

Sorry I did not read the question more carefully and used part a) for everything.
 
  • #39
No Problem!
 

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